Create a real ToolchainContext for TransitionsOutputFormatterCallback.

Part of work on execution transitions, #7935.

Closes #8121.

PiperOrigin-RevId: 245228413
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/ConfiguredTargetFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/ConfiguredTargetFunction.java
index 0c3961e..9e24416 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/ConfiguredTargetFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/ConfiguredTargetFunction.java
@@ -459,7 +459,7 @@
    * Returns the target-specific execution platform constraints, based on the rule definition and
    * any constraints added by the target.
    */
-  private static ImmutableSet<Label> getExecutionPlatformConstraints(Rule rule) {
+  public static ImmutableSet<Label> getExecutionPlatformConstraints(Rule rule) {
     NonconfigurableAttributeMapper mapper = NonconfigurableAttributeMapper.of(rule);
     ImmutableSet.Builder<Label> execConstraintLabels = new ImmutableSet.Builder<>();